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CalculatorBuddy

Stair Calculator

Calculate stair rise, run, step count, angle, stringer dimensions, tread adjustments, and headroom for basic or comprehensive layouts.

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Basic — Use One Run

ExampleSample values — edit any field to see your result.

Results update as you type.

Valid stair layouts

13–26 possible runs

Estimated result

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Stair layout candidates

RunsRisesRiseTotal runStringer lengthStringer heightAngle
13149.84 inches or 25.00 cm10 feet 7.95 inches or 325.00 cm15 feet 0.95 inches or 459.62 cm10 feet 7.95 inches or 325.00 cm45.00°
14159.19 inches or 23.33 cm11 feet 5.8 inches or 350.00 cm15 feet 8.49 inches or 478.76 cm10 feet 8.61 inches or 326.67 cm43.03°
15168.61 inches or 21.88 cm12 feet 3.64 inches or 375.00 cm16 feet 4.18 inches or 498.29 cm10 feet 9.18 inches or 328.13 cm41.19°
16178.11 inches or 20.59 cm13 feet 1.48 inches or 400.00 cm17 feet 0.01 inches or 518.18 cm10 feet 9.69 inches or 329.41 cm39.47°
17187.66 inches or 19.44 cm13 feet 11.32 inches or 425.00 cm17 feet 7.97 inches or 538.42 cm10 feet 10.14 inches or 330.56 cm37.87°
18197.25 inches or 18.42 cm14 feet 9.17 inches or 450.00 cm18 feet 4.07 inches or 558.97 cm10 feet 10.54 inches or 331.58 cm36.38°
19206.89 inches or 17.50 cm15 feet 7.01 inches or 475.00 cm19 feet 0.27 inches or 579.81 cm10 feet 10.91 inches or 332.50 cm34.99°
20216.56 inches or 16.67 cm16 feet 4.85 inches or 500.00 cm19 feet 8.58 inches or 600.93 cm10 feet 11.23 inches or 333.33 cm33.69°
21226.26 inches or 15.91 cm17 feet 2.69 inches or 525.00 cm20 feet 5 inches or 622.29 cm10 feet 11.53 inches or 334.09 cm32.47°
22235.99 inches or 15.22 cm18 feet 0.54 inches or 550.00 cm21 feet 1.5 inches or 643.88 cm10 feet 11.8 inches or 334.78 cm31.33°
23245.74 inches or 14.58 cm18 feet 10.38 inches or 575.00 cm21 feet 10.08 inches or 665.68 cm11 feet 0.05 inches or 335.42 cm30.26°
24255.51 inches or 14.00 cm19 feet 8.22 inches or 600.00 cm22 feet 6.74 inches or 687.67 cm11 feet 0.28 inches or 336.00 cm29.25°
25265.3 inches or 13.46 cm20 feet 6.06 inches or 625.00 cm23 feet 3.47 inches or 709.85 cm11 feet 0.5 inches or 336.54 cm28.30°
26275.1 inches or 12.96 cm21 feet 3.91 inches or 650.00 cm24 feet 0.26 inches or 732.18 cm11 feet 0.69 inches or 337.04 cm27.41°
Valid stair layouts13–26 possible runs
Plan a stair flight from one tread run or a total run and the floor-to-floor rise. Basic mode compares practical step counts; comprehensive mode adds fixed rise or step count, tread thickness, headroom, and stringer mounting.

How to use this calculator

Measure the total floor-to-floor rise before choosing the stair dimensions. Check the calculated number of risers and treads, then review the diagram. Confirm local requirements for riser height, tread depth, landings, and headroom before construction.

Examples

Basic 25 cm run and 3.5 m rise

The candidate table spans 13 through 26 runs. At 13 runs there are 14 rises of 25 cm, 325 cm total run, a 459.62 cm stringer, and a 45° angle. These are geometric candidates, not approved layouts.

Comprehensive 20 cm target rise

For a 3.5 m total rise and 25 cm run, the layout has 17 steps, a 20 cm regular rise, 10 cm first step, 425 cm total run, and 538.08 cm stringer length.

Formula

rise = total rise ÷ number of risers

total run = one run × number of runs

stringer length = √(total run² + stringer height²)

angle = atan(rise ÷ run)

Building-code requirements vary by location and occupancy. Verify the final layout, structure, headroom, handrails, landings, and permitted tolerances with your local authority or a qualified professional.

Code and measurement limits

The US Access Board stairway guide shows why geometry alone is insufficient: covered stairs require uniform risers and treads and address surfaces, nosings, and handrails. Its dimensions apply to facilities within that standard's scope and are not a substitute for the residential, building, fire, or accessibility rules governing a particular project. Measure finished floor elevations and finished tread surfaces. The calculator does not design stringer strength, connections, landings, guards, handrails, or foundations.

Frequently asked questions

What are stair rise and run?
Rise is the vertical distance from the top of one tread to the next. Run is the horizontal depth of one step, excluding or accounting for nosing as required by the design.
Why is there usually one more riser than run?
The upper floor acts as the final tread, so a flight commonly has one fewer horizontal runs than vertical rises.
How is stringer length calculated?
It is the hypotenuse formed by total run and stringer height, using the Pythagorean theorem.
Can I build directly from these measurements?
Treat them as planning values. Local codes govern maximum riser height, minimum tread depth, headroom, landings, guards, handrails, and structural design.

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